The effects of pharmacological and behavioral manipulations on cigarette smoking in normal human volunteers will be studied. Research will be conducted both with inpatients in a residential research ward setting, and with outpatients in an outpatient setting. One major set of experiments will explore pharmacological effects on smoking by examining the effects of ethanol, pentobarbital, chlorpromazine and caffeine. The second major set of experiments will focus on behavioral aspects of cigarette smoking. Several experiments will investigate the extent to which the relative reinforcing efficacy of smoking is influenced by manipulating cigarette dose (i.e., puffs/cigarette) and nicotine dose (i.e., nicotine dose/cigarette). These studies will assess relative reinforcing efficacy with progressive-ratio schedules and choice procedures. Several other experiments will explore how the scheduling of environmental events may influence smoking behavior. One experiment will examine the suppression of cigarette smoking by contingent time-out procedures. Other experiments will study cigarette smoking as an adjunctive behavior by exploring the extent to which the scheduling of environmental events may induce or drive cigarette smoking. Throughout the proposed experiments, the self-administration behavior will be monitored by counting the number of cigarettes smoked, and by measuring the frequency, size and duration of individual cigarette puffs with a specially constructed device. A carbon monoxide analyzer will be used to provide a physiological measure of amount of cigarette smoking. Overall, these studies should provide an improved understanding of the addictive process by describing the interactive relations among pharmacological and behavioral variables influencing smoking.